Methods and apparatus for the thermal treatment of mixed urban wastes

ABSTRACT

The invention concerns a device for the thermal transformation of waste, in particular mixed urban waste. It comprises conveyor means, housed in an enclosed space, for discharging waste into a furnace having inductively heated zones of successively higher temperatures. Gases and oils produced by pyrolysis are removed at stages of the process.

RELATED APPLICATIONS

This application claims priority of Swiss patent application Nos. 00588/19 and 00589/19, both filed on May 2, 2019.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for the thermal treatment of waste materials, in particular urban trash and garbage. More specifically, the invention relates to methods and apparatus for the anaerobic pyrolysis of waste, and the production thereby of organic gases and liquids that are useful as fuels and feedstocks. Even more specifically, the invention relates to the gasification by thermal treatment of mixed waste, in particular urban waste containing synthetic materials, organic waste, vegetable waste and the like.

BACKGROUND

The disposal of urban waste is a problem in cities all over the world. Accumulations of improperly disposed of solid wastes are invading oceans, beaches and rural sites in many countries, and the problem is prompting government and private efforts to initiate techniques and procedures to avoid destructive effects on environmental resources, agriculture and fisheries. Urban waste is heterogeneous by nature, and the recovery of products from the waste requires, under most of the proposed treatment conditions, a preliminary sorting which is inefficient, costly and tedious to implement. Indeed, the sorting of household waste, which represents an extremely large quantity of waste and includes products of often doubtful quality, often does not enable the sorted materials to be recovered, and the sorting operations are rarely profitable.

In many areas, the recovery of waste involves the use of technologies which are too inconsistent to be widely implemented, and the temporary disposal of waste still too often consists either in burying it, i.e. temporarily masking it, or in partially destroying it, for example by incineration.

The recycling of certain separated materials, such as paper, metal, glass, and plastics, can reduce the volume of the waste, but the required sorting operations are costly and inefficient, and enormous volumes of non-recycled materials still remain to be disposed of.

Landfilling and incineration are becoming increasingly costly, and cause serious damage to the environment through water and air pollution. Not only is the correction of environmental damage resulting from the use of landfill or incineration techniques expensive, it is not an effective and sustainable solution, and it is economically inefficient for the cities and countries that implement these processes. Current methods for the production of electrical and thermal energy from waste are limited, and rely for the most part on incineration. This rarely provides a cost-effective solution for the populations that produce such waste.

The technology of transforming organic wastes by pyrolysis is unquestionably a positive approach to the problem, particularly when the process releases little or no greenhouse gases such as CO₂ and methane. Current methods, however, are net consumers of energy, due for the most part to the presence of water in urban waste. This has led to the limitation of pyrolytic methods to the recovery of fuel from tires, plastics, and dehydrated biomass from forestry and agriculture.

Waste treatment equipment remains highly segmented for specific applications, and the treatment units are extremely complex and excessively costly in terms of energy consumption and maintenance costs. At present, pyrolysis furnaces, which remain the most application-oriented, are made for specific applications and are, for the most part, unable to produce, from mixed waste materials, transformation products for specific applications at satisfactory costs.

There remains a need for methods and equipment capable of converting urban and other organic waste into feedstocks and fuels in solid, liquid or gaseous form, without CO2 or other greenhouse gas emissions.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, the invention provides a generalized thermal treatment of mixed waste, that allows very precise temperature zones to be determined in identified treatment furnace sectors, preferably via the use of induction heating systems. This process offers economic advantages by eliminating, to a large extent, the difficulties of sorting, and avoids the recovery of products with a low basic quality whose recovery is a priori difficult.

According to the present invention, waste is fed into at least one confined site, in the absence of oxygen, with a view to treating it to obtain transformed products, in which a substantial reduction in their humidity is carried out before and during their penetration into said confined site, and in which a gradual rise in temperature is carried out, in predetermined temperature zones, and in that, during the continuous movement of said waste, its vertical settlement by gravity is carried out in said confined site in said predetermined temperature zones.

The invention also concerns a device for the thermal transformation of waste, in particular urban waste, in particular organic waste, vegetable waste, synthetic materials or the like, comprising means of transport for bringing the waste into at least one confined site, in the absence of oxygen, with a view to treating it to obtain transformed products, comprising preheating means for effecting a substantial reduction in their humidity before and during their penetration into said confined site, heating means for effecting a gradual rise in temperature in predetermined temperature zones, and compacting means for effecting, during the continuous movement of said waste, its vertical compacting by gravity in said confined site through said predetermined temperature zones.

The present invention proposes to overcome these disadvantages by implementing a process, as defined in the preamble, which responds to all the problems encountered in the transformation of waste, in particular household or similar waste, into transformed products having a real economic value and capable of being stored without degrading, having a real energy value and delivering a minimum of greenhouse gases, in particular CO2, when used as fuel.

To this end, the said gradual rise in temperature of the said waste is carried out, in zones of predetermined temperatures, by independent electrical induction heating means arranged specifically in each of the said zones of predetermined temperatures, and in that the said processed products are evacuated at outlets of the said confined site, after the thermal transformation of the said waste according to the treatment temperatures, in a gaseous, liquid or solid form.

According to a preferred form of manufacture, said increase in the temperature of said waste is effected by heating heat transfer elements which are in direct contact with said waste to be thermally treated and which transmit at least part of their heat thereto.

According to a form of advantageous realization, said heat-transferring elements comprise wall elements of said confined site, which is traversed by said waste to be heat-treated in the course of its movement.

Preferentially, temperature zones are determined corresponding to temperature ranges at which it is planned to raise the temperature of said waste to be thermally transformed as a function of the transformed products to be obtained.

In a particularly advantageous manner, the temperature of the waste to be treated is raised to a first dehydration value, which is substantially between 100 and 250° C., and preferably between 150 and 200° C., then to a second roasting value substantially between 200 and 450° C. and preferably between 250 and 400° C., then to a third pyrolysis value substantially between 300 and 900° C. and preferably between 250 and 800° C.

Advantageously for the treatment of relatively diverse household waste, processed products resulting from the transformation of the waste are collected in the form of combustible gases, in the form of combustible oils and in the form of solid particles, substantially free of CO2.

Also for this purpose, the device according to the invention is characterized in that said means for heating said waste by zones of predetermined temperatures, comprise at least one electrical induction heating equipment, specific to each of said predetermined temperatures, said equipment being independent and, disposed specifically in each of said zones of predetermined temperatures, and in that the device comprises evacuation means arranged to evacuate said transformed products at selective outlets of said confined site, after the specialized thermal transformation of said waste.

In a particularly advantageous manner, the device may advantageously comprise at least one furnace, which contains said confined space into which the waste to be transformed is poured, wherein the furnace consists of a tower partly of cylindrical shape, and a central core positioned symmetrically inside the tower, induction heating means positioned, at least partly, in a first cylindrical space delimited along an outer wall of said tower and said confined space, through which said waste to be thermally transformed passes during its transformation.

The predetermined temperature zones are preferably delimited by horizontal sectors positioned from top to bottom, in the direction of movement of the wastes during their transformation, which each comprise induction heating means capable of generating an increasing temperature with respect to the preceding one corresponding to that of the preceding predetermined temperature zone.

The wall of the central core is advantageously a magnetisable material, preferably of iron or an iron alloy.

The outer wall of said tower is advantageously made of a non-magnetic material, in particular aluminium or an aluminium-based alloy.

The outer wall of said tower is preferably made of a magnetizable material, preferably of iron or an iron alloy.

The induction heating means are preferably partly positioned in the annular space between the outer wall of the tower and the inner wall of said tower and in that the complementary induction heating means are housed in said central core.

The furnace is constructed according to the principle of nestable sectors, each of the components of which corresponds to a predetermined temperature zone, and in that the components of each individual part of the furnace consist of a central sector comprising a central core element, a furnace wall element and a set of electric coils arranged to constitute the induction heating means corresponding to the predetermined temperature zone concerned.

In summary. the present invention proposes to overcome the disadvantages of the known prior art, by providing means for processing urban waste delivered in mixed and summarily sorted form, in particular without recyclable materials that can be easily separated such as metals, glass or used batteries, with organic waste and all other organic waste. In this form, it is possible to produce a solid fuel that allows the massive storage of energy, both electrical, after combustion to power a generator, and thermal. The fuel is transportable as required and can be used in conventional burners or converted into heat and electricity by cogeneration. Part of the solid fuel produced can be used to power all the installations according to the invention, for its production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a schematic view which illustrates the process and an advantageous form of realization of a device for transforming urban waste according to the invention.

FIG. 2 represents a longitudinal cross-sectional view of a second form of construction of a device for transforming urban waste according to the invention.

FIG. 2 is a cross-sectional view of the municipal waste processing facility in FIG. 2.

FIG. 4 represents a longitudinal section view of a third form of construction of a device for transforming urban waste, comprising a plurality of waste transformation furnaces, according to the invention.

FIG. 5 represents a schematic realization form of a mixed waste gasification device for a basic installation, advantageously intended for a domestic application,

FIG. 6 represents a first variant for the realization of a cost-effective installation of mixed waste gasification equipment for a first collection center for the gases obtained by thermal treatment,

FIG. 7 represents a third variant for the realization of an advantageous installation of mixed waste gasification devices for a second collection center for the gases obtained by thermal treatment, and

FIG. 8 shows a third variant for the implementation of a cost-effective mixed waste gasification plant for a third collection center for gases obtained by thermal treatment.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures, and in particular to FIG. 1, the waste processing device 10 is arranged to process household waste 100, which consists of, inter alia, municipal waste, in particular organic waste, vegetable waste, plastics, e.g. thermoplastics or the like, into processed products with a reusability, e.g. in the form of combustible products or products with a usable own functionality. Device 10 comprises on the one hand conveyor means 21, housed in a closed space 22, which may be a conduit or channel or the like, into which said waste 100 is fed by said conveyor means 21 for discharge into at least one confined site 23. The space 22 is closed, preferably in a sealed manner, to avoid the presence of the waste with air or oxygen and may contain means to reduce its moisture content, in the form of vibrators or the like or any other suitable means.

The processing device 20 furthermore comprises at least one furnace 24, which contains the confined space 23 receiving the waste 100 to be processed. In very general terms, furnace 24 consists of a partly cylindrical tower 24 a with an outer wall 24 b. Inside the tower 24 a there is a central core 25, which is positioned symmetrically inside the tower 24 a and which is closed so as not to leave any open space through which the waste 100 can pass, and a substantially cylindrical inner wall 24 c is mounted parallel to the outer wall 24 b of the tower 24 a, to define a first cylindrical space 24 d in which are interposed electrical coil circuits 26, 27, 28, in particular which correspond to predetermined temperature zones T1, T2, T3 of the furnace 24, as will be explained in more detail below. The inner wall 24 c of the cylindrical space 24 d leaves at the periphery of the central core 25 a second cylindrical space which constitutes said confined space 23, through which said waste 100 to be thermally transformed passes.

In the example shown, confined space 23 has a cylindrical cross-sectional shape. However, this one-piece cylindrical space could be constructed in several cylindrical sections arranged in parallel, for example for waste heating purposes, in the passage areas which would then consist of parallel sectors surrounding the central core 25.

The furnace 24 and the central core 25 are, as mentioned above, composed of three sectors T1, T2, T3, but which could be supplemented by complementary sectors Tn-1 and Tn, having different temperatures from those of sectors T1, T2 and T3. Furthermore, as shown in FIG. 1, a complementary sector of electric coil circuit 35 could be arranged inside central core 25, in the lower part of the furnace 24, which corresponds to the hottest zone of predetermined temperatures, which is for example sector T3. The complementary circuit of electric coils 35 could for example be arranged in the wall of the central core 25.

In the lower part of the furnace 24, three receiving sectors for processed products have been shown. These are, for example, an outlet 40 for liquid products such as oil, an outlet 41 for gases such as synthetic gases and an outlet 42 at the base of furnace 24 for solid processed products such as carbon black or roasted pellets or similar. The processed products are dependent on the nature of the waste being processed in processing temperature zones. Further details shall be set forth in the description of the process according to the invention.

A particularly advantageous form of construction is that furnace 24 could be built according to a principle of nestable sectors, each of which corresponds to a predetermined temperature zone, as originally planned. The components of each individual part of furnace 24 consist of a central sector 35 a, 35 b, 35 c etc., comprising a central core element 35, a wall element 24 a, 24 b, 24 c etc. of furnace 24 and an electrical coil circuit element 26, 27, 28 etc . . . arranged to constitute the heating means corresponding to the relevant predetermined temperature zone T1, T2, T3, etc . . . In this case, furnace 24 would have a modular design and its maintenance and servicing could be carried out in a simple and effective manner by simply replacing the defective part. The number of independent modules in this case corresponds to the number of individual units that define the predefined temperature zones.

With regard to the sectors of the furnace 24 whose heating means are controlled by induction, it should be noted that the central core 25 is made of a ferrous, magnetizable material which reacts to induced electric currents. It is placed in the heart of furnace 24. 24. As a result, the mass of waste to be treated is in direct contact with the hot mass, which increases the efficiency and homogeneity of the heating. In fact, the presence of the central core 25 is added to the presence of the inner wall 24 c also made of a ferrous material, magnetizable, reacting to the induced electric currents, to heat the waste 100 to be transformed.

In addition, the induction heating system, which acts remotely within the magnetic fields by the generation of induced electric current, does not demand no special maintenance as it does not come into contact with the waste by transit.

The waste processing mode 100, defined by the process, is as follows. During its circulation in the conveying means 21, waste 100 preferably has a temperature between 70 and 90° C. Subsequently, it undergoes a vertical settling by the effect of gravity and following its partial dehydration on the conveyor means 21, housed in the closed space 22. This dehydration is essential to the greatest extent possible in order to avoid the production of non-condensable greenhouse gases such as CO2. They enter the confined site 23 to be subjected to predefined temperatures, in the temperature zones T1, T2, and T3, or T1, T2, T3, Tn-1 and Tn. which are gradually increasing from top to bottom. In order to improve and promote the dewatering of the waste 100, a drying hopper can supplement the means of transport or can be arranged in the first predetermined temperature zone T1 to raise the temperature of the waste to a first value which can, for example, be between 100 and 250° C., and preferably between 150 and 200° C. Subsequently, zone T2, called the roasting zone, can be arranged so that the temperature is set substantially between 200 and 450° C. and preferably between 250 and 400° C. A third temperature zone, called the pyrolysis zone, having a temperature between 300 and 900° C. and preferably between 250 and 800° C. could be provided in the oven of device 10.

A preferred operating procedure is that the chain of operations required under the process for the invention initially comprises at least partial dehydration waste 100, heated to an uncontrolled temperature of between 50 and 100 degrees and preferably between 70 and 90° C., in order to remove part of the free water, thus a significant proportion of oxygen present in the mass of waste to be treated.

Subsequently, drying is carried out at a controlled temperature, with the waste 100 through the first predetermined temperature zone. The energy supplied comes in part from the recovery of waste heat from other operations of the system. Any additional heat is supplied by electrical induction heating.

Temperature-controlled roasting by induction of the oven allows the temperature of the waste 100 to be raised to around 200-450° C. and preferably between 250-400° C. Part of the energy required comes from heat recovery through other thermal waste treatment operations. The second phase of treatment proposed by the innovation is the roasting of the materials to be treated directly following the first treatment or in a delayed manner depending on production needs.

The last operating phase concerns thermal treatment by pyrolysis, which is carried out at temperatures that are significantly between 400 and 800° C., but which could evolve according to the needs and the waste to be processed.

The products can be delivered in non-condensed gaseous form such as for example the following gases : CH4, C2H4, H2, CO, CO2, or in condensed form, for example pyrolysis oils, which can be used as fuel to drive an electric generator or in the form of solid residues such as carbon black, pellets that can be used to generate heat or bio-tank, which can be used in the agricultural field.

FIGS. 2 and 3 show views of another form of construction of a device 50 designed to process mixed municipal or similar waste. Device 50, like device 10, consists of essentially the same elements, constructed and assembled on somewhat different bases. The transformation device 50 comprises at least one furnace 54, which contains a confined space 53 receiving the waste 100 to be transformed. The furnace 54, like the furnace 20 shown in FIG. 1, consists of a tower 54 a having an outer wall 54 b and inside which a central core 55 is arranged, which is closed in such a way that no open space is left through which the waste 100 can pass, and an inner wall 54 c is mounted parallel to the outer wall 54 b of the tower 54 a, in order to arrange electrical circuits 56, 57, 28 or more which correspond to predetermined temperature zones T1, T2, T3 of the furnace 54. As before, a second cylindrical space which constitutes said confined space 53, is arranged to be traversed by said waste 100 to be thermally transformed. At the various outlets of the confined space 53, respectively 60, 61 and 62 are collected from one by liquids, for example oils, gases and solids, similar to those mentioned in the description of FIG. 1.

The cross-sectional view of FIG. 3 of the device in FIG. 2 along the cutting axis M-M, shows that the construction of furnace 50, close to the construction of furnace 24 in FIG. 1, is substantially cylindrical, with conical and/or frustoconical inlet and outlet sectors. The superposition of the three essential sectors can be seen, the electrical sector with the electrical circuit components responsible for the production of predetermined heat in the predetermined temperature zones, this sector being defined between the outer wall 54 a of furnace 50 and its inner wall 54 c; the waste passage sector 100, namely the confined space 53 and the central core 55.

FIG. 4 represents a generalization form of the device 50 with n units arranged in series. All the units 50 are arranged side by side under a closed feed duct 22 for waste 100 to be heat treated following its passage through the confined spaces 53 arranged around the central cores 55. At the outlet of each of the treatment units, the processed waste 100 is collected in the form of liquids, more particularly combustible oils, gases and solid substances at outlets 60, 61 and 62 respectively.

Theoretically the treatment temperature zones could be modified by one of the units 50, 51 . . . n-1, n. For example, one of the units could be mainly or entirely concerned at very high temperatures with the aim of carrying out mainly or exclusively a treatment of waste by pyrolysis. Another unit could be specialized in roasting treatment in order to increase profitability in larger units.

With reference to FIG. 5, the mixed waste gasification plant 100 consists of a tank 11 containing a mixed waste mass 12 and a gasification furnace 20. The mixed waste is introduced in the raw state from the top of tank 11, which has a lid 13 at the top. The mixed waste 12 is mixed with a quantity of liquid material 14 which is discharged into tank 11 through a pipe 15 which communicates with a first opening 21 connected to the gasification furnace 20. The lower part of tank 11, which is advantageously truncated cone-shaped, has a double jacket 16 of similar shape, which contains in particular induction heating elements 17 and forms a sealed space 18 in which air flows from a mouth 22 connected to the gasification furnace 20 near its upper end. The heating elements 17 are integrated in an induction heating environment with side walls made of magnetizable materials and have the function of at least partially drying the mixed waste 12, which contains sufficient moisture, to allow the transfer and circulation of the mixed waste 12 to the gasification furnace 20.

The lower part of tank 11 is connected by an inner pipe 19 to the central part 23 of the gasification furnace 20, which consists of the central part 23, which is substantially cylindrical and is surrounded by an annular space 24 having two walls, an outer wall 24 a and an inner wall 24 b. The annular space 24 contains a plurality of electric wire coils 25 which are electric induction heating elements arranged to raise the temperature of the central portion 23, as well as the inner wall 24 b, to mixed waste gasification heat treatment temperatures 12. At its upper part, the gasification furnace 20 has a conical or frustoconical sector 26, towards which the gases which are produced in the central part 23 of the gasification furnace 20 are concentrated. The central part 23 may have an opening 30 which leads to a flare 26 a of the type known as a Bunsen burner which allows a certain quantity of the gases produced by gasification to be burnt. This combustion by a burner may, for example, take place in a kind of boiler 27, the outer wall of which 28 may be coiled up in a winding of pipes 29, for example to heat a heat transfer fluid and to transmit reusable thermal energy for appropriate use. Two further openings 30 a, and 22 are provided in the upper part of the gasification furnace 20 for collecting on the one hand the gasification gases of the mixed waste 12 for use in a cogeneration unit 50, suitable for producing electrical energy, and on the other hand 22, which supplies air, produced during the gasification process of the mixed waste 12, into the furnace 20.

The storage enclosure, e.g. tank 11 for mixed waste 12 and the gasification furnace 20 are connected to each other by the central duct 19. The central duct 19 is surrounded by the sealed space 18 and the annular space 24, both of which contain electrical induction heating elements 17 and 25 respectively. Duct 22, which discharges air into the sealed space 18 surrounding tank 11, conveys this air, preferably with the assistance of a blower, e.g. a fan 31 or similar.

The entry of the mixed waste 12 into the central duct 19 is assisted by a propulsion which is exerted by a screw or mixer 32 which is housed in the initial part of the central duct 19 and which is preferably driven in rotation by an electric motor 33 or similar. This assembly causes a substantially continuous displacement of the waste 12 to the gasification furnace 20.

The device described 100 can be realized in a relatively simple way for almost domestic use, which has the advantage of transforming into thermal energy and/or electrical energy all domestic waste 12, agricultural, comprising materials as diverse as paper, synthetic materials or domestic waste, meat, without the need for prior sorting. It can also be used on a larger scale, possibly even with prior selective sorting, to treat large volumes of collected waste produced by a much larger population. Depending on the types of waste concerned, specific treatment phases may be used to increase the profitability of the resulting processed products. Facilities can be designed according to the uses, the volumes of mixed waste producers and the processed products sought.

Such designs correspond to the devices in FIGS. 6, 7 and 7. FIG. 6 shows a plant 200 comprising a gasification furnace 20, which is substantially identical to that in FIG. 5, and a series of tanks 11 a, 11 b to 11 n all containing mixed waste 12. Tanks 11 to 11 n are substantially identical to tank 11 in FIG. 5, but may have different dimensions depending on requirements, including the number of inhabitants in a given area and uses. In this design, mixed waste 12 may be identical, but may also be more specific and correspond to more specific or sectorized materials. Such a situation may occur if the waste to be gasified has initially undergone a pre-sorting process that allows for the definition of waste categories, or if it is envisaged to modulate the products to be obtained according to the treatment temperatures to be applied.

A selective sorting of mixed wastes 12, for example, would make it possible to create a tank containing primarily or exclusively synthetic materials, in particular polyethylenes, polypropylenes and/or polymethylenes. Another tank could essentially contain organic materials of plant origin or agricultural or forestry materials. In these cases, selective heat treatment would allow the production of distinct gases according to the pyrolysis temperatures applied, resulting in an improvement in the final efficiency of the use of the gases obtained. Such a facility is well suited for a relatively large mixed waste collection unit and is well structured with regard to the use of the gases obtained after pyrolysis treatment.

It should be noted that tanks 11 a, 11 b, 11 n are all connected to the gasification furnace by a central duct 19 whose function is to bring the mixed waste 12 into the central part 23 of the gasification furnace 20. As for the device in FIG. 5. air is sent from the upper area of the central part 23 of the gasification furnace 20 into a channel that surrounds the central duct 19. Water is also injected into tanks 11 a, 11 b, 11 n to fluidize the mass of mixed waste and facilitate its circulation towards the gasification furnace 20. The central duct 19 has a series of valves 60 that control the flow of mixed waste 12 from the different tanks 11 a, 11 b, 11 n to the gasification furnace 20.

FIG. 7 shows a device 300 consisting of a tank 11, connected to several gasification furnaces 20 a, 20 b, 20 n, all connected to tank 11 by a central duct 19, which is supplied with mixed waste 12 through valves 61. The individual components of Plant 200 are essentially identical to those of Plant 100 in FIG. 5. The size of tank 11 may possibly be larger depending on the average amount of waste 12 collected. In such a design, each of the gasification furnaces can be designed to perform the gasification heat treatment at a given pyrolysis temperature, which is the most appropriate for the selected waste products. The aim is essentially the same as for the plant in FIG. 6, i.e. to adapt the pyrolysis heat treatment to the products to be treated in order to obtain the best efficiency of the plant.

FIG. 8 shows a gasification plant 400 with n gasification furnaces 20 a . . . , 20 n-1, 20 n and n tanks, respectively 11 a . . . 11 n-1, 11 n, for mixed waste 12. Device 400 is a synthesis of installations 200 and 300 and is particularly suitable for the thermal treatment by pyrolysis of a mixed waste collection unit 12 which can contain all types of waste, of private origin, such as so-called household waste, of artisanal origin, such as vegetable waste, of public origin such as paper, packaging, synthetic materials, textiles or others. The collection and storage of waste can be organized, sorting can be carried out in a structured way, storage can be selective according to habits or regulations. The 400 device shown in FIG. 8 is able to adapt to all the rules with the aim of producing a raw material that can be used to supply energy and electrical power, in the best conditions and with the best economic efficiency, using low-value waste. All the mixed waste contained in all the tanks 11 a, . . . 11 n-1, 11 n can be fed through the central duct 19 to any of the gasification furnaces of 20, . . . 20 n-1, 20 n. The tanks can be structured in any way and the gasification furnaces can be adapted so that the product resulting from the treatment, essentially gas, can be obtained under the best conditions in the most economical way.

The operating process of gasification plant 100 initially consists of recovering waste 12 in tank 11. These mixed wastes, which in particular contain household waste, are very varied and can have extremely diverse consistencies, especially since water or liquids 14 from the pyrolysis furnace 20 are added to ensure a certain fluidity to the mass, in order to pass through the mixer 32 and advance it into the central pipe 19. The electric heating coils 17, which are part of the induction heating circuits, heat the mass of waste 12 to raise its temperature in order to cause at least partial drying or dehydration of the waste.

The temperature of the waste can be substantially between 50 and 100° C. and preferably between 70 and 90° C.

In the central part 23 of the gasification furnace 20, the temperature can reach substantially temperatures of the order of 30 to 60° C., or even 70° C. in the lower sector T1, temperatures of the order of 60 to 400° C., or even 450° C. in the sector T2 and temperatures of the order of 400 to 850° C., or even 100° C. in the upper part T3, of the central part 23. An oxygen supply at burner 26 a, which is comparable to a Bunsen burner, raises the flame temperature of the burnt gases to approx. 1500 to 1800° C. This burner can be used, for example, to generate hot water which is conveyed through the ducts 29 of boiler 27, to be used appropriately according to local demand.

The gases from device 100, according to the gasification process, can be fed into the planned cogeneration system 50 either directly or after a storage period which is an indirect way of storing electrical energy, other than charging it on battery cells. The cogeneration unit, which is preferably equipment that can produce electric power using the gases produced by the gasification of mixed waste 12, can be adapted as required and started up at the time of a request for the use of electric power.

Dehydration of the material to be treated is essential to the greatest extent possible in order to avoid the production of non-condensable greenhouse gases such as CO2. Condensed material from gasification, if not fully treated in a first pass, can be returned to the waste collection tank for mixing with the incoming material.

The gasification operations are carried out in gasification furnace 20 at temperatures between 400 and 1000° C. and preferably between 450 and 850° C. The outer wall 24 b of the central part 23 of the gasification furnace 20 is made of a ferrous material, reacting to possible induced electric currents, surrounding the mass to be treated, thus allowing it to be heated homogeneously.

Various variants could be imagined by the man of the art, as regards the realization and the layout of the mixed waste gasification equipment. However, the invention corresponds to the forms of realization defined by the claims and to those which illustrate the process and the use of the gases obtained.

Various variants could be imagined by the man of the art as regards the construction and arrangement of the temperature zones of the device, but they remain included in the characteristics defined by the claims. The system described is a priori used to manufacture solid fuel as well as fuels in liquid or gaseous form in order to bring hot thermal and electrical energy to consumers from urban waste and other organic waste. However, it is of course possible to modify the production parameters according to the specific needs of users and consumers. 

We claim:
 1. A process for the thermal transformation of waste, in particular urban waste, in particular organic waste, vegetable waste, synthetic materials or the like, in which the said waste is fed into at least one confined site, in the absence of oxygen, with a view to treating it in order to obtain transformed products, in which a substantial reduction in its humidity is carried out before and during its penetration into the said confined site, and in which a gradual rise in temperature is carried out, in zones of predetermined temperatures, and in that this is done in the course of the continuous movement of the said waste, to their vertical settling by gravity in said confined site, through said zones of predetermined temperatures, characterized in that said gradual rise in temperature of said waste is carried out, in zones of predetermined temperatures, by independent electrical induction heating means disposed specifically in each of said zones of predetermined temperatures and in that said transformed products are evacuated at outlets of said confined site, after the thermal transformation of said waste according to the treatment temperatures, in gaseous, liquid or solid form.
 2. The process according to claim 1, characterized in that the said increase in temperature of the said waste is carried out by heating heat-transferring elements which are in direct contact with the said waste to be heat-treated and which transmit at least part of their heat thereto.
 3. Process according to claim 1, characterized in that the temperature of the waste to be treated is first raised to a dehydration value, which is between 100 and 250° C., then raised to a roasting value between the dehydration value and 450° C., and then raised to a pyrolysis value between roasting value and 900° C.
 4. Process according to claim 3, characterized in that products from the processing of the waste are collected in the form of combustible gases which are substantially free of CO₂, in the form of combustible oils, and in the form of solid particles.
 5. A device for the thermal transformation of waste comprising one or more of household waste, agricultural waste, and synthetic materials, comprising transport means for bringing said waste into at least one confined site, in the absence of oxygen, with a view to thermally treating it in order to obtain transformed products, the device comprising drying means for effecting a substantial reduction in their humidity before and during their penetration into said confined site, heating means for effecting a gradual rise in temperature, in zones of predetermined temperatures, and compacting means for effecting during the continuous movement of said waste, to their vertical settling by gravity in said confined site, through said zones of predetermined temperatures, characterized in that said means for heating said waste comprises at least one electrical induction heating means, specific to each predetermined temperatures, said induction heating means being independent and, disposed specifically in each of said zones of predetermined temperatures, and in that the device comprises evacuation means arranged to evacuate said transformed products at selective outlets of said confined site, after the thermal transformation of said waste.
 6. The device according to claim 5, characterized in that it comprises at least one furnace, which contains said confined space into which the waste to be transformed is poured, wherein the furnace comprises a tower partly of cylindrical shape, and a central core, positioned symmetrically inside the tower, induction heating means positioned, at least partially, in a first cylindrical space delimited along an outer wall of said tower and said confined space, through which said waste passes during its transformation.
 7. The device according to claim 5, characterized in that the predetermined temperature zones are delimited by horizontal sectors positioned from top to bottom, in the direction of movement of the waste during its transformation, each of which zone comprises induction heating means capable of generating a temperature which increases with respect to the previous zone.
 8. The device according to claim 5, characterized in that the wall of the central core is a magnetizable material.
 9. The device according to claim 5, characterized in that the outer wall of said tower is made of a non-magnetic material.
 10. The device according to claim 5, characterized in that the outer wall of said tower is a magnetizable material.
 11. The device according to claim 5, characterized in that the induction heating means are positioned at least partly in the annular space between the outer wall of the tower and the inner wall of said tower, and in that complementary induction heating means are housed in said central core.
 12. The device according to claim 5, characterized in that the furnace is constructed according to the principle of nestable sectors, each of the components of which corresponds to a predetermined temperature zone and in that the components of each individual part of the furnace are composed of a central sector comprising a central core element, a wall element of the furnace and a set of electric coils arranged to constitute the heating means corresponding to the predetermined temperature zone concerned.
 13. A device for the gasification by thermal treatment of mixed waste, in particular municipal waste containing synthetic materials or the like, organic waste, vegetable waste or the like, characterized in that the gasification device comprises at least one transit tank into which said mixed waste is supplied, and at least one gasification furnace which communicates with said at least one transit tank, wherein said at least one transit tank has heating means for at least partially dehumidifying the mixed waste, wherein said at least one mixed waste gasification furnace comprises heating means for at least partially converting said mixed waste into combustible gases and wherein said at least one transit tank and said at least one mixed waste gasification furnace are connected to each other by a central duct which at least partially surrounds, a first sealed space through which air flows from an opening of the gasification furnace and which communicates with a second annular space containing electric induction heating elements arranged to raise the temperature of the gasification furnace and the mixed waste to cause said gasification of said mixed waste.
 14. The device for gasification of mixed waste according to claim 13, characterized in that said first sealed space contains heating elements for heating the mixed waste contained therein to a temperature sufficient to remove moisture and cause partial dehumidification of said mixed waste.
 15. The device for the gasification of mixed waste according to claim 14, characterized in that the heating elements are induction heating means which are distributed in sectors to define temperature zones of the mixed waste to be heat-treated.
 16. Device for gasification of mixed waste according to claim 13, characterized in that the central part of said at least one furnace for gasification of said mixed waste comprises an opening arranged to evacuate water and in that said opening is connected to a mouth which opens into said at least one transit tank for discharging said liquids onto said mixed waste.
 17. The device for gasification of mixed waste according to claim 13, characterized in that said central part of said at least one furnace for gasification of said mixed waste comprises an opening arranged to evacuate air and in that said opening is connected to said first sealed space, peripheral to the lower part of said at least one tank.
 18. The device for gasification of said mixed waste according to claim 13, characterized in that said central part of said at least one furnace for gasification of said mixed waste comprises an opening arranged to evacuate gas obtained by the pyrolysis of said mixed waste by thermal treatment, and in that said opening is connected to a cogeneration device.
 19. The device for gasification of said mixed waste according to claim 13, characterized in that said central part of said at least one furnace for gasification of said mixed waste comprises an opening arranged to transport gas obtained by the pyrolysis of said mixed waste by thermal treatment and in that said opening corresponds to a torch for supplying heat to a heat-transfer fluid.
 20. The device for gasifying said mixed waste according to claim 13, characterised in that said arrangement comprises a plurality of tanks for storing mixed waste and a single gasification furnace, said single gasification furnace being connected point-wise to all of said tanks of said plurality of tanks, by means of at least one central conduit and in that said at least one central conduit comprises connection valves for selectively unblocking the connection of each of said storage tanks for waste mixed with said gasification furnace.
 21. The device for gasification of said mixed waste according to claim 13, characterized in that said arrangement comprises a plurality of gasification furnaces and a single mixed waste storage tank, said single mixed waste storage tank being connected point-wise to all of said gasification furnaces of said plurality of furnaces, through at least one central conduit and in that said at least one central conduit has connection valves for selectively unblocking the connection of each of said storage tank for waste mixed with said plurality of said gasification furnaces.
 22. The device for gasifying said mixed waste according to claim 13, characterized in that said device comprises a plurality of gasification furnaces and a plurality of mixed waste storage tanks, each of said mixed waste storage tanks of said plurality of mixed waste storage tanks being point-connected to each of said gasification furnaces of said plurality of furnaces, through at least one central conduit and in that said at least one central conduit has connection valves for selectively unblocking the connection of each of said waste storage tank mixed with said plurality of said gasification furnaces.
 23. A process for the gasification, by thermal treatment, of mixed waste comprising household waste, characterized in that said mixed waste is brought into at least one transit tank which communicates with at least one gasification furnace, in that said mixed waste is heated in said at least one tank to dehumidify it at least partially, in that said mixed waste is transferred into said at least one gasification furnace which comprises heating means for at least partially converting it into combustible gases, by means of a central duct which at least partially surrounds a first sealed space in which air flows from a mouth of the gasification furnace and which communicates with a second annular space containing electric induction heating elements arranged to raise the temperature of the gasification furnace and the mixed waste to cause said gasification of said mixed waste, characterized in that said mixed waste is heated sequentially in sectors by induction heating means which are arranged to bring the mass of mixed waste to be heat treated to temperatures between 400 and 1000° C. 